1. Field of the Invention
This invention relates to a CCD type solid-state imaging device in which signal charges are transferred by means of transfer electrodes. More particularly, it relates to an interline transfer or frame interline transfer type solid-state imaging device.
2. Description of the Related Art
A CCD image sensor usually has a plurality of photosensor regions arrayed on the surface of a silicon substrate, and is so constructed that signal charges generated in these regions are transferred out of a chip to produce image signals.
This type of the CCD image sensor known in the art is constructed as shown in FIG. 1, in which a plurality of photosensor regions 2 consisting of n-type impurity-diffusion regions are formed on the surface of a p-type silicon substrate 1. Signal charges are generated in each of the these photosensor regions 2 isolated from the photosensor regions 2 neighboring thereon in the vertical direction or in a direction shown by an arrow V in FIG. 1. On top of a region isolating the neighboring photosensor regions 2 from each other are formed a first transfer electrode layer 4 and a second electrode layer 5, with interposition of an insulating layer 3, for establishing connection with neighboring vertical charge transfer sections. On top of the second transfer electrode 5 is formed an aluminum light-barrier layer 7 with interposition of a second insulating layer 6. This light-barrier layer 7 is formed for surrounding a region around the photosensor region 2 and an aperture 8 formed in the light-barrier layer 7 faces the photosensor region,
With this type of the CCD image sensor, the light incident via aperture 1 is converted in the photosensor region 2 into signal charges which are transferred and outputted as image signals.
The above described conventional CCD image sensor, however, has a drawback that low smear cannot be realized due to electrical charges from a vertical pixel isolation region 9.
That is, some of the incident light through aperture 1 is incident obliquely to generate signal charges in the vertical pixel isolating region 9. The charges thus generated in the vertical pixel isolating region 9 descend down the hill of potential towards the vertical charge transfer section 10 to flow into the vertical charge transfer section 10, thus producing smear to lower the quality of the video signals,
In the JP Patent Publication KOKAI No. 62-221147 (1987), there is disclosed a technique wherein the light-barrier layer is formed up to the lateral side of a step region to reduce the smear. However, charge generation in the vertical pixel isolating region cannot be suppressed sufficiently by simply covering the step region with the light-barrier layer,